Abstract: Objective: To examine changes in social support during early recovery after acute myocardial infarction (AMI) and determine whether these changes influence outcomes within the first year.Methods: Among 1951 AMI patients enrolled in a 19-center prospective study, we examined changes in social support between baseline (index hospitalization) and 1month post-AMI to longitudinally assess their association with health status and depressive symptoms within the first year. We further examined whether 1-month support predicted outcomes independent of baseline support. Hierarchical repeated-measures regression evaluated associations, adjusting for site, baseline outcome level, baseline depressive symptoms, sociodemographic characteristics, and clinical factors.Results: During the first month of recovery, 5.6% of patients had persistently low support, 6.4% had worsened support, 8.1% had improved support, and 80.0% had persistently high support. In risk-adjusted analyses, patients with worsened support (vs. persistently high) had greater risk of angina (relative risk=1.46), lower disease-specific quality of life (β=7.44), lower general mental functioning (β=4.82), and more depressive symptoms (β=1.94) (all p≤.01). Conversely, patients with improved support (vs. persistently low) had better outcomes, including higher disease-specific quality of life (β=6.78), higher general mental functioning (β=4.09), and fewer depressive symptoms (β=1.48) (all p≤.002). In separate analyses, low support at 1month was significantly associated with poorer outcomes, independent of baseline support level (all p≤.002).Conclusion: Changes in social support during early AMI recovery were not uncommon and were important for predicting outcomes. Intervening on low support during early recovery may provide a means of improving outcomes.